The present invention relates to a magnetic tape drive installed with a magnetic head to apply a magnetic field to a magnetic tape by making contact with the moving magnetic tape.
An example of a thin film magnetic head for a magnetic tape drive of the related art is shown in FIG. 7 viewed from the side rubbed by the magnetic tape. FIG. 7 shows that the thin film magnetic head for a magnetic tape drive of the related art has a composite thin film magnetic head 1 comprised of a read element 10 enclosed by an insulator layer 4 and a write element 20 installed approximately in parallel with a read element 10, and further has a composite thin film magnetic head 2 having the same structure as the composite thin film magnetic head 1 and arrayed in the symmetrical reverse of the composite thin film magnetic head 1.
A shield member 6 is sometimes installed between the composite thin film magnetic head 1 and the composite thin film magnetic head 2 to prevent mutual interference during the write or the read operations of the composite thin film magnetic head 1 and composite thin film magnetic head 2. Here, the read gap 11 of the read element of the composite thin film magnetic head 1 and composite thin film magnetic head 2 and the longitudinal write gap 21 of the write element, form a right angle relative to the drive direction A of the magnetic tape.
A typical high density magnetic pattern written by utilizing the structure for a thin film magnetic head for a magnetic tape drive is shown in FIG. 8. The track 2nxe2x88x921 and the track 2n+1 are written from right to left by the composite thin film magnetic head 2. The track 2n and the track 2n+2 are written from left to right by the composite thin film magnetic head 1.
The composite thin film magnetic head 1 and composite thin film magnetic head 2 are installed on an actuator driven by a step motor and a voice coil motor. The composite thin film magnetic head 1 must be positioned directly over the track 2n by actuator drive when the composite thin film magnetic head 1 is reading the magnetic pattern of the track 2n. However, the accuracy of the mechanical positioning is deficient due to variations in part dimensions during manufacture such as in the actuator drive shaft and the step motor. There is therefore a certain probability that an offset (or deviation) of the composite thin film magnetic head 1 from the track 2n by an amount equal to angle xcex4 will occur.
In the structure of the related art, the longitudinal read gap 11 of the composite thin film magnetic head 1 is largely parallel (approximately parallel to the track width) to the longitudinal magnetic transition 27 of the magnetic pattern of the track 2n+1, so that no azimuth loss will occur during read-out of the magnetic pattern of track 2n+1, and the read output obtained from the track 2n+1 magnetic pattern will be noise on the read output of track 2n, and overlap onto the read output of track 2n. As a result, the read output detector circuit of the magnetic tape drive will mistakenly detect the noise caused by the track 2n+1 magnetic pattern, as the signal obtained from the track 2n magnetic pattern, thus causing the problem that the magnetic pattern correctly written on track 2n cannot be read-out.
A method was contrived to sufficiently narrow the width of the track for the magnetic conversion element so that the read gap will not interfere with the track 2n+1 even if for instance, the positioning of the composite thin film magnetic head 2 has a xcex4 offset. This method is at least effective and is widely utilized.
The read output of this technology of the related art however, is proportional to the track width of the magnetic conversion element, thus creating the new problem that the more the track width of the magnetic conversion element is narrowed, the lower the read output becomes. The greater the write density in particular becomes, the narrower the track width so that there is a limit on how much the track width of the magnetic conversion element can be narrowed and still maintain the signal-to-noise (S/N) ratio of the read signal and this problem becomes more obvious as the write density increases.
In view of the above problems with the related art, this invention has the main object of providing a thin film magnetic head for a magnetic tape drive to correctly read out, even if off-track, the high density magnetic patterns written on the magnetic tape without picking up noise from adjacent tracks, even if a phenomenon occurs such as a magnetic head not positioned at the correct position (off-track condition) caused by a TMR (track miss registration) involving the mechanical positioning precision.
To achieve the above objectives, an example of the related art had a thin film magnetic head for a magnetic tape drives consisting of two composite thin film magnetic heads each having an azimuth angle. However when using this head to read-out a magnetic pattern (FIG. 8) written with the head of the related art shown in FIG. 7, even if the mechanical positioning was precise, an azimuth loss occurred even if the position of the magnetic head 1a was not offset versus the specified track, thus causing the problem that the magnetic pattern of the specified track could not be read out with a high signal-to-noise (SN) ratio.
This invention therefore has another main objective of providing a thin film magnetic head for a magnetic tape drive to correctly read out high density magnetic patterns written on magnetic tape, with no deterioration in the read signal-to-noise (SN) ratio, even if the magnetic pattern (FIG. 8) was written with a head of the related art as shown in FIG. 7.
To achieve the above objects, a thin film magnetic head for a magnetic tape drive of this invention, utilized in magnetic tape drives to read and write computer data comprises:
a first composite thin film magnetic head to read and write information on a first track of a magnetic tape, along with a read element and write element with a mutual parallel read gap and a write gap,
and a second composite thin film magnetic head to read and write information on a second track adjacent to a first track and having a read element and write element, with a mutual parallel read gap and a write gap,
and the read gap and the write gap of the first composite thin film magnetic head form a right angle versus the drive direction of the magnetic tape, and the read gap and the write gap of the second composite thin film magnetic head form an oblique (xcex8) angle versus the drive direction of the magnetic tape.
The thin film magnetic head for a magnetic tape drive of this invention preferably satisfies the relation of an angle theta (xcex8) greater than 70xc2x0 and less than 90xc2x0.
A thin film magnetic head for a magnetic tape drive of this invention, has the first and second composite thin film magnetic heads arrayed in a row in the tape drive direction.
A thin film magnetic head for a magnetic tape drive of this invention, has first and second composite thin film magnetic heads in a row, with respectively a read element installed on the inner side and a write element installed on the outer side respectively in the tape drive direction.
Another thin film magnetic head for a magnetic tape drive of this invention, has first and second composite thin film magnetic heads in a row, with respectively a read element installed on the outer side and a write element installed on inner side respectively in the tape drive direction.
Another thin film magnetic head for a magnetic tape drive of this invention, has the first and second composite thin film magnetic heads installed in a row intersecting the tape drive direction.
Another thin film magnetic head for a magnetic tape drive of this invention, further comprising: a third composite thin film magnetic head to read and write information on the first track, along with a read element and a write element having a read gap and a write gap in parallel with a read gap and a write gap of the first composite thin film magnetic head; and a fourth composite thin film magnetic head to read and write information on the second track, along with a read element and a write element having a read gap and a write gap in parallel with the read gap and a write gap of the second composite thin film magnetic head.
Another thin film magnetic head for a magnetic tape drive of this invention, has the first and third composite thin film magnetic heads are installed in a row in the tape drive direction, the second and fourth composite thin film magnetic heads are installed in a row in the tape drive direction, and the first and second composite thin film magnetic heads are installed in a row intersecting the tape drive direction, and the third and fourth composite thin film magnetic heads are installed in a row intersecting the tape drive direction.
A characteristic feature of the thin film magnetic head for a magnetic tape drive of this invention, comprising at least two composite thin film magnetic heads is that an azimuth angle is provided in the read gap and write gap of at least one of the composite thin film magnetic heads, and by installing the other composite thin film magnetic heads with read gaps and write gaps at right angles to the drive direction of the magnetic tape, read-out compatibility can be maintained with other equipment of the related art, and the read out performance can be improved when off-track.
As shown in FIG. 2 of the thin film magnetic head for a magnetic tape drive of this invention in FIG. 1, an angle theta xcex8 is provided in the longitudinal read gap and the longitudinal write gap (hereafter simply read gap and write gap) of the composite thin film magnetic head la relative to the drive direction A of the magnetic tape and further, an angle of 90xc2x0 is provided in the longitudinal read gap and the longitudinal write gap of the composite thin film magnetic head 2a relative to the drive direction of the magnetic tape. Therefore, the magnetic transition of the even tracks and the magnetic transition of the odd tracks form a relative angle (90xc2x0xe2x88x92xcex8) on the magnetic pattern written on the magnetic tape with this head. So even if the head is not accurately positioned on the specified track, and the position is offset in the direction of the adjacent track (direction of tape width), the head fulfills its role and due to the effect of azimuth loss, reads out only the magnetic pattern of the specified track. Therefore, the read operation can be performed correctly, even if the accuracy of the mechanical position is poor, or the head is offset to a position in the direction of the adjacent track. Magnetic patterns written with a head of the related technology can also be accurately read out by utilizing the head 2a.